Abstract
This document presents the physics case and ancillary studies for the proposed CODEX-b long-lived particle (LLP) detector, as well as for a smaller proof-of-concept demonstrator detector, CODEX-beta , to be operated during Run 3 of the LHC. Our development of the CODEX-b physics case synthesizes ‘top-down’ and ‘bottom-up’ theoretical approaches, providing a detailed survey of both minimal and complete models featuring LLPs. Several of these models have not been studied previously, and for some others we amend studies from previous literature: In particular, for gluon and fermion-coupled axion-like particles. We moreover present updated simulations of expected backgrounds in CODEX-b’s actively shielded environment, including the effects of shielding propagation uncertainties, high-energy tails and variation in the shielding design. Initial results are also included from a background measurement and calibration campaign. A design overview is presented for the CODEX-beta demonstrator detector, which will enable background calibration and detector design studies. Finally, we lay out brief studies of various design drivers of the CODEX-b experiment and potential extensions of the baseline design, including the physics case for a calorimeter element, precision timing, event tagging within LHCb, and precision low-momentum tracking.
Highlights
1.1 MotivationNew Physics (NP) searches at the Large Hadron Collider (LHC) and other experiments have primarily been motivated by the predictions of variousPage 3 of 47 1177 CODEX-β CODEX-b LS 2 Production Run 3Install data taking Removal Partial Install LS3 CODEX-b
Primary achievements of the experimental program include the discovery of the Higgs boson [1,2], the ongoing investigation of its interactions [3], and remarkable precision Standard Model (SM) measurements
A compelling category of such signatures are long-lived particles (LLPs), which generally appear in any theory containing a hierarchy of scales or small parameters, and are ubiquitous in beyond the Standard Model (BSM) scenarios
Summary
The Large Hadron Collider (LHC) provides unprecedented sensitivity to short-distance physics. The primary LHC experiments (ATLAS, CMS, LHCb, ALICE) have proven to be remarkably versatile and complementary in their BSM reach. The central challenge in detecting LLPs is that their masses and their lifetimes may span many orders of magnitude In this expression of interest we advocate for CODEX-b (“COmpact Detector for EXotics at LHCb”), a LLP detector that would be installed in the DELPHI/UXA cavern next to LHCb’s interaction point (IP8). We discuss the timetable for the construction and data taking of CODEXβ, and show that it may achieve new reach for certain BSM scenarios
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